The present invention relates generally to transfer members useful in imaging components, for use in electrostatographic, including digital, apparatuses. The transfer layers herein are useful for many purposes including layers for transfer films such as intermediate transfer, transfix or transfuse films, and the like. More specifically, the present invention relates to a transfer component having a three-layer configuration. In particularly preferred embodiments, the transfer component has a) an electrically controlled stiff or rigid substrate, b) an electrically controlled conformable intermediate layer, and c) a thin, low friction outer layer. In a another preferred embodiment, the outer layer is a thin fluoropolymer layer. The three-layer transfer component of the present invention may be useful in films used in xerographic machines, especially color machines.
In a typical electrostatographic reproducing apparatus such as an electrophotographic imaging system using a photoreceptor, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of a developer mixture. One type of developer used in such printing machines is a liquid developer comprising a liquid carrier having toner particles dispersed therein. Generally, the toner is made up of resin and a suitable colorant such as a dye or pigment. Conventional charge director compounds may also be present. The liquid developer material is brought into contact with the electrostatic latent image and the colored toner particles are deposited thereon in image configuration. Another type of developer uses xe2x80x9cdryxe2x80x9d or powder toner particles with developer beads as the carrier for the toner particles.
The developed toner image recorded on the imaging member can be transferred to an image receiving substrate such as paper via an intermediate transfer member. Alternatively, the developed image can be transferred to an intermediate transfer member from the image receiving member via another transfer member. The toner particles may be transferred by heat and/or pressure to an intermediate transfer member, or more commonly, the toner image particles may be electrostatically transferred to the intermediate transfer member by means of an electrical potential between the imaging member and the intermediate transfer member. After the toner has been transferred to the intermediate transfer member, it can then be transferred to the image receiving substrate, for example by contacting the substrate with the toner image on the intermediate transfer member under heat and/or pressure. Alternatively, the developed image can be transferred to another intermediate transfer member such as a transfix/transfuse or transfer member. A transfix or transfuse member uses heat associated with the transfer member in order to both transfer and fix or fuse the developed image to a copy substrate.
Intermediate transfer members, including transfix or transfuse members, enable high throughput at modest process speeds. In four-color photocopier systems, the transfer member also improves registration of the final color toner image. In such systems, the four component colors of cyan, yellow, magenta and black may be synchronously developed onto one or more imaging members and transferred in registration onto a transfer member at a transfer station. Additional colors may be used, thereby requiring more than four color stations.
In electrostatographic printing machines it is desired that the transfer of the toner particles from the transfer member to any subsequent intermediate transfer members or, alternatively, to the final image receiving substrate be very high, preferably substantially 100 percent. Less than complete transfer to the image receiving substrate results in image degradation and low resolution. Highly efficient transfer is particularly important when the imaging process involves generating full color images since undesirable color deterioration in the final colors can occur when the color images are not efficiently transferred from the transfer member.
Thus, it is desired that the transfer member surface have excellent release characteristics with respect to the toner particles. Conventional materials known in the art for use as transfer member layers often possess the strength, conformability and electrical conductivity necessary for use as transfer members, but can suffer from poor toner release characteristics. When heat is associated with a transfer member, such as in the case of a transfix member, the transfix member should also ideally possess good thermal conductivity in addition to superior release characteristics.
In addition, it is desired that the transfer member have sufficient toughness to undergo multiple cycling during use. Moreover, the outer layer of the transfer member should be chemically compatible with the toner to be used, and with paper with which the layer will come in contact. In known electrophotostatographic machines, diketones are normally used in paper and toner components. Therefore, it is desired that the transfer outer layer be compatible with diketones and other components of toner and paper.
U.S. Pat. No. 6,118,968 discloses an intermediate transfer member comprising a plastic or polyimide substrate, an intermediate adhesive such as a polyurethane solventless adhesive, and an outer polyphenylene sulfide layer.
U.S. Pat. No. 5,998,010 discloses a transfer member comprising a plastic substrate having an adhesive intermediate layer of epoxy resins or polysiloxanes, and an outer release layer of a polymer having more than one type of carbon black dispersed therein. The polymer of the outer layer can be a polyimide, a urethane or a silicone.
U.S. Pat. No. 5,761,595 discloses a three-layer intermediate transfer member having a plastic substrate, a fluorinated carbon filled fluoroelastomer intermediate layer, and an outer silicone release layer.
U.S. Pat. No. 5,361,126 discloses an imaging apparatus including a transfer member including a heater and pressure-applying roller, wherein the transfer member includes a fabric substrate and an impurity-absorbent material as a top layer. The impurity-absorbing material can include a rubber material.
U.S. Pat. No. 5,337,129 discloses an intermediate transfer component comprising a substrate and a ceramer or grafted ceramer coating comprised of integral, interpenetrating networks of haloelastomer, silicon oxide, and optionally polyorganosiloxane.
U.S. Pat. No. 5,340,679 discloses an intermediate transfer component comprised of a substrate and thereover a coating comprised of a volume grafted elastomer, which is a substantially uniform integral interpenetrating network of a hybrid composition of a fluoroelastomer and a polyorganosiloxane.
U.S. Pat. No. 5,456,987 discloses an intermediate transfer component comprising a substrate and a titamer or grafted titamer coating comprised of integral, interpenetrating networks of haloelastomer, titanium dioxide, and optionally polyorganosiloxane.
In tandem color systems, multiple images are transferred from a photoconductive surface to an intermediate transfer member. In some systems, the images are subsequently transferred from the intermediate transfer member to a transfix or transfuse member. The transfix or transfuse member transfers the developed images to a copy substrate and fuses the image thereto, thereby forming a permanent image on the copy substrate. Because of these multiple cycles, it is desired that there be low friction between the transfer member and the photoconductive member. Although it can be made to be very small, it is desired that some amount of differential velocity between the transfer member and the photoreceptor typically be accommodated in electrostatographic systems, due to drives and mechanical tolerances. This low friction allows some amount of differential velocity between the photoreceptor and the transfer member without substantially impacting image quality. It is further desired that the transfer member, for example, a transfer belt, not elastically stretch during multiple cycling. Therefore, in color registration, a sufficiently laterally rigid substrate is desired for the transfer member. However, single layer rigid transfer belts lead to a very high local pressure acting on high pile height toner images during, for example, transfer to the intermediate transfer member. For certain high toner and photoconductor adhesion conditions, this can lead to what is referred to as a xe2x80x9chollow characterxe2x80x9d transfer defect.
For transfer members, a conformable rubber overcoating such as a silicone on top of a rigid substrate can relieve the hollow character problem during transfer to the intermediate layer. However, experiments have shown that such rubber coatings have a tendency to create high transfer of background particles off the imaging substrate. Such rubber coatings can significantly reduce the ability to achieve high transfer efficiency off of the intermediate at a low or a moderate temperature, and they create high friction between the intermediate belt and the imaging drums.
Therefore, it is desired to provide a transfer member that has high transfer off the intermediate transfer member without increasing background transfer. It is further desired to provide a transfer member that has low friction, which is desired to allow some amount of slip in the transfer zones. Another desired quality of a transfer member is allow for minimizing the magnitude of the local pressure acting on high pile height lines, thereby preventing hollow character defect. A further desired quality for transfer member, is obtaining a high degree of conformance in the transfer zones in order to reduce air gaps between the toner images on the photoreceptor and the transfer member, thereby reducing air breakdown issues and enhancing transfer. A further desired quality of a transfer member is to allow for printing on rough surfaces such as cardboard boxes, paper towels, and like rough surfaces.
The present invention provides, in embodiments: a transfer member comprising, a) a rigid substrate, b) a conformable intermediate layer positioned on the rigid substrate, and c) a thin fluoropolymer layer positioned on the conformable intermediate layer, wherein the fluoropolymer is selected from the group consisting of tetrafluoroethylene, perfluoroalkoxy, fluorine ethylene propene, polymers thereof, and mixtures thereof.
The present invention further provides, in embodiments: a transfer member comprising, a) a rigid substrate, b) a conformable intermediate layer positioned on the rigid substrate, c) a thin fluoropolymer layer positioned on the conformable intermediate layer, wherein the fluoropolymer is selected from the group consisting of tetrafluoroethylene, perfluoroalkoxy, fluorine ethylene propene, polymers thereof, and mixtures thereof, and d) a heating member associated with the rigid substrate.
In addition, the present invention provides, in embodiments: an image forming apparatus for forming images on a recording medium comprising, a) a charge-retentive surface to receive an electrostatic latent image thereon; b) a development component to apply a developer material to the charge-retentive surface to develop the electrostatic latent image to form a developed image on the charge-retentive surface; c) a first transfer member for transferring the developed image from the charge-retentive surface to a second transfer member or to a copy substrate, the first transfer member comprising, i) a rigid substrate, ii) a conformable intermediate layer positioned on the rigid substrate, and iii) a thin fluoropolymer layer positioned on the conformable intermediate layer, wherein the fluoropolymer is selected from the group consisting of tetrafluoroethylene, perfluoroalkoxy, fluorine ethylene propene, polymers thereof, and mixtures thereof.